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Configure uid/gid maps from child and not parent #23

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Configure uid/gid maps from child and not parent #23

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40 changes: 40 additions & 0 deletions src/child.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -70,6 +70,46 @@ pub unsafe fn child_after_clone(child: &ChildInfo) -> ! {
}
}

if !child.uid_maps.is_empty() {
let fd = libc::openat(libc::AT_FDCWD, b"/proc/self/uid_map\0".as_ptr() as *const i8, libc::O_WRONLY);
if fd < 0 {
fail(Err::SetIdMap, epipe);
}
if libc::write(fd, child.uid_maps.as_ptr() as *const libc::c_void, child.uid_maps.len()) < 0 {
fail(Err::SetIdMap, epipe);
}
if libc::close(fd) < 0 {
fail(Err::SetIdMap, epipe);
}
}

if !child.gid_maps.is_empty() {
// first configure setgroups to "deny"
let fd = libc::openat(libc::AT_FDCWD, b"/proc/self/setgroups\0".as_ptr() as *const i8, libc::O_WRONLY);
if fd < 0 {
fail(Err::SetIdMap, epipe);
}
let deny = b"deny";
if libc::write(fd, deny.as_ptr() as *const libc::c_void, deny.len()) < 0 {
fail(Err::SetIdMap, epipe);
}
if libc::close(fd) < 0 {
fail(Err::SetIdMap, epipe);
}

// then write gid_map
let fd = libc::openat(libc::AT_FDCWD, b"/proc/self/gid_map\0".as_ptr() as *const i8, libc::O_WRONLY);
if fd < 0 {
fail(Err::SetIdMap, epipe);
}
if libc::write(fd, child.gid_maps.as_ptr() as *const libc::c_void, child.gid_maps.len()) < 0 {
fail(Err::SetIdMap, epipe);
}
if libc::close(fd) < 0 {
fail(Err::SetIdMap, epipe);
}
}

// Move error pipe file descriptors in case they clobber stdio
while epipe < 3 {
let nerr = libc::fcntl(epipe, F_DUPFD_CLOEXEC, 3);
Expand Down
35 changes: 18 additions & 17 deletions src/run.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -52,6 +52,8 @@ pub struct ChildInfo<'a> {
pub pid_env_vars: &'a [(usize, usize)],
pub keep_caps: &'a Option<[u32; 2]>,
pub pre_exec: &'a Option<Box<Fn() -> Result<(), io::Error>>>,
pub uid_maps: &'a [u8],
pub gid_maps: &'a [u8],
}

fn raw_with_null(arr: &Vec<CString>) -> Vec<*const c_char> {
Expand Down Expand Up @@ -239,6 +241,20 @@ impl Command {
let setns_ns = self.config.setns_namespaces.iter()
.map(|(ns, fd)| (to_clone_flag(*ns), fd.as_raw_fd()))
.collect::<Vec<_>>();
let mut uid_maps = Vec::new();
let mut gid_maps = Vec::new();
if let Some(&(ref uids, ref gids)) = self.config.id_maps.as_ref() {
if self.id_map_commands.is_none() {
for map in uids {
writeln!(&mut uid_maps, "{} {} {}",
map.inside_uid, map.outside_uid, map.count).unwrap();
}
for map in gids {
writeln!(&mut gid_maps, "{} {} {}",
map.inside_gid, map.outside_gid, map.count).unwrap();
}
}
}
let pid = try!(result(Err::Fork, clone(Box::new(|| -> isize {
// Note: mo memory allocations/deallocations here
close(wakeup.take().unwrap().into_fd());
Expand All @@ -258,6 +274,8 @@ impl Command {
pid_env_vars: &pid_env_vars,
keep_caps: &self.keep_caps,
pre_exec: &self.pre_exec,
uid_maps: &uid_maps,
gid_maps: &gid_maps,
};
child::child_after_clone(&child_info);
}), &mut nstack[..], self.config.namespaces, Some(SIGCHLD as i32))));
Expand Down Expand Up @@ -325,23 +343,6 @@ impl Command {
cmd.arg(format!("{}", map.count));
}
try!(cmd_result(Err::SetIdMap, cmd.status()));
} else {
let mut buf = Vec::new();
for map in uids {
writeln!(&mut buf, "{} {} {}",
map.inside_uid, map.outside_uid, map.count).unwrap();
}
try!(result(Err::SetIdMap,
File::create(format!("/proc/{}/uid_map", pid))
.and_then(|mut f| f.write_all(&buf[..]))));
let mut buf = Vec::new();
for map in gids {
writeln!(&mut buf, "{} {} {}",
map.inside_gid, map.outside_gid, map.count).unwrap();
}
try!(result(Err::SetIdMap,
File::create(format!("/proc/{}/gid_map", pid))
.and_then(|mut f| f.write_all(&buf[..]))));
}
}
if let Some(ref mut callback) = self.before_unfreeze {
Expand Down